Photographic bleach-out layer



June 15, 1943. s. s. FIERKE EI'AL 2,322,005

PHOTOGRAPHIG BLEACH-OUT LAYER Filed Dec. 26, 1940 ELuE SENSITIVE EMULSION CONTAIN/N6 DISPERSED YELLOW DYE PARTICLES.

DISPERSED CYAN DYE PARTICLES.

SUPPORT.

Jc'HEL/R/Nca 5. F/ERKE PAUL M V/TTL/M L. 07' 5., MLDER INVENTORS BY ;M

A TTORNEYS ?atented June 35. 1%43 iii a 2,322,005 PHOTOGRAPHIC BLEACH-OUT LAYER Scheuring S. Fierke, Paul W.

S. Wilder, Rochester, N. Y.,

Vittum, and not assignors to Eastman Kodak Company, Rochester, N. Y., a corporation of New Jersey Application December 26, 1940, Serial No. 371,684 in Great Britain December 29, 1939 2 Claims.

This invention relates to color photography and more particularly to the incorporation of dyes in silver halide emulsion layers to be subjected to bleaching for the formation of colored images.

Processes of color photography are well known in which dyes are incorporated in silver halide emulsion layers and after formation of silver images in the layers the dyes are bleached in the region of the silver images or in the region of silver halide images. One of the difliculties encountered in this process is that of securing adequate dye density in the layers without undesirable crystallization of the dyes or without diffusion of the dyes from the layers in which they are incorporated in multi-layer coatings.

It is, therefore, an object of the present invention to provide a method for incorporating bleachable dyes in silver halide emulsion layers. A further object is to provide a method for preventing diffusion of dyes from photographic layers in bleach-out processes. A still further object is to provide a means for securing dyed layers of adequate density in which the dyes are not subject to crystallization or diffusion. Other objects will appear from the following description of our invention.

- These objects are accomplished by dissolving the dye to be incorporated in the emulsion layer in one or more organic solvents each of which is substantially water-insoluble and at least one of which is high boiling. The solution of the dye in these solvents is then emulsified in an aqueous solution and is mixed with the sensitive emulsion.

In the accompanying drawing the single figure is a sectional view of a multi-layer photographic element having dyes incorporated in the emulsion layers according to our invention.

In the manufacture of bleach-out layers for color photography, the sensitive material is composed of silver halide grains dispersed in a suitable water-soluble or water-permeable colloidal material such as gelatin, agar, polyvinyl phthalate or water-soluble cellulose esters. The dye incorporated in this emulsion is dissolved in a second carrier which is immiscible with the colloidal material or carrier composing the layer and this second carrier containing the dye is added to the colloid of the sensitive layer in-the form of highly dispersed particles. By the proper selection of the carrier or solvent for the "dye. is possible to incorporate the necessary concentrations of dye in the desired high degree of dispersion and to have the dye in such physical state that it is incapable of diffusing from the layer in which it is incorporated. At the same time, the dye is held in a sufilciently loose state of physical combination with the. emulsions that it is available for chemical or physical reaction necessitated for bleaching to form a dye image in the layer. r

In the preferred embodiment of our invention the dye is dissolved in a low boiling organic solvent and a high boiling organic solvent is added to this solution. Both of these solvents must be substantially water-insoluble so that a dispersion of the mixture of dye and solvents in water'can be formed. In certain'cases the dye can be dissolved in the high boiling solvent alone since both the high boiling solvent and the low boiling solvents are solvents for the dye. The solution of dye in the solvent or solvents is emulsified in water containing a wetting agent or in a dilute gelatin solution to form a dispersion of the dye and the solvent or solvents in the aqueous solution. The low boiling solvent present is then preferably removed by heating and the dispersion added to the emulsion which is then coated on a suitable support.

Dyes suitable for use in our process include azo I dyes capable of being bleached in the region of a silver image and soluble in organic solvents such as butyl acetate. Vat dyes such as anthraquinone dyes soluble in organic solvents may also be used.

The following examples, which are illustrative only, indicate methods of incorporating dyes in emulsion layers according to our invention:

Example 1 0.05 gram of Oil Red 0 (Schultz, Farbstofftabellen, No. 92) was dissolved in 2.0 cc. of trio-cresyl phosphate and 3.0 cc. of butyl acetate. This solution was poured into 80cc. of water containing 0.2 g. of Gardinol WA and homogenized by circulating through a colloid mill. The butyl acetate was subsequently evaporated as described in the examples connected with bleachable filter dyes, and the final volume of cc. was diluted to cc. with water and added to cc.

of a moderate-speed high-contrast positive-type emulsion. Plates were coated. Using a hydrochloric acid bleach bath described below the bleaching was satisfactory, although slightly incomplete in the highlights.

Bleach bath. Hydrochloric acid (concentrated) cc 100.0 Sodium chloride gms 100.0 Potassium bromide --gms 30.0 Dimethyl quinoxaline -gln 0.3 Oxyaminophenazine -gm..- 0.02 Waterto cc 1000.00

Example 2 The dispersion described in Example 1 was repeated using the same dye but without evaporation of the butyl acetate, and when tested under similar conditions was somewhat more coarse than the dispersion described in Example l, but otherwise showed very similar properties. Example 3 0.1 gram of the triphenyl guanidine salt of Alcol Fast Red 48L (sold by Modern Chemical Co., Canastota, N. Y.) was dissolved in 2.0 cc. of butyi acetate and 5.0 cc. of acetone, and 2.0 cc. of tri-o-cresyl phosphate. This solution was added t 85 cc. of water containing 0.2 gram of Gardinol WA, and was homogenized by circulating through a colloid mill. The lowboiling organic solvents were evaporated from the resulting dispersion until the total volume was 60 cc. This also removed a very appreciable quantity of water in attempting to drive off the the support It or any suitable material such as cellulose ester or paper is coated with layers ll, l2 and I3 comprising gelatino-silver halide emulsion layers sensitive respectively to the red. green and blue. regions of the spectrum and having particles of dyes and water-insoluble solvent incorporated in the emulsion layers according to our invention. For the red sensitive emulsion layer a cyan dye may be used, for the green sensitive emulsion layer a magenta dye such as 011 Red 0 is suitable, and for the blue-sensitive layer a yellow dye such as benzene azo ,resorcinol may be used. The particles of dye and water-insoluble solvent are only a few microns in diameter, although in the drawing they are enlarged with respect to the thickness of the emulsion layers for purposes of representation.

The examples and compounds described in the present specification are illustrative only and it is to be understood that our invention is limited only by the scope of the appended claims.

We claim:

1. The method of incorporating in a gelatinosilver halide layer a dye capable of being bleached in the region of a photographic image, which comprises mixing the dye with a volatile substantially water-insoluble organic solvent for the dye and trlcresyl phosphate, emulsifying the dye and trlcresyl phosphate in an aqueous solution. dispersing the emulsion as liquid particles in the gelatino-silver halide emulsion and coating it on a support.

2. The method of incorporating in a gelatino silver halide layer an azo dye capable of being bleached in the region of a silver image which comprises mixing the dye with butyl acetate and trlcresyl phosphate, emulsifying the solution of the dye and trlcresyl phosphate in an aqueous solution containing-a wetting agent, evaporating the butyl acetate and a portion of the water from the emulsion, adding the emulsion to the gelatino silver halide emulsion and coating it on a support;

SCHEURING S. FIERKE. PAUL W. VIT'I'UM. LOT S. WILDER. 

